Legal experts say it’s likely special counsel Robert Mueller secretly gained access to the National Rifle Association’s tax returns as part of the investigation into Russian meddling in the 2016 election, according to a McClatchy report.

Mueller’s team is reportedly looking into NRA donors with links to Russia and investigating whether some donors used the organization to illegally funnel foreign money to President Trump’s campaign.

The NRA spent $30 million backing Trump in the 2016 presidential election.